The pursuit for fuel alternatives to conventional fossil fuels is primarily driven by the need for a ‘clean’ emissions fuel coupled with low production costs and wide availability. Much attention is paid to the environmental impact of fuel emissions. Research into alternative fuels focuses on fuels that will reduce the amount of particulate matter and oxides produced by fuel combustion as well as fuels that reduce the non-combusted fuel and CO2 emissions and other products of combustion.
Fuel alternatives for complete or partial replacement of traditional fuels have not become widely used.
One major disadvantage with the complete replacement of traditional fuels, and in particular fuels for compression ignition engines (diesel fuels), with a renewable replacement fuel, relates to the perceived problems associated with the low cetane index of such fuels. Such fuels present problems for achieving ignition in the manner required for efficient operation of the engine.
The present applicant has developed new fuel compositions for use in compression ignition (diesel) engines with an improved emissions profile without a major adverse impact on fuel efficiency and/or engine performance. The fuel composition is a two-part fuel composition, with a main part based on methanol and water, which is introduced into the combustion chamber of the engine, and a fumigant comprising an ignition enhancer, such as dimethyl ether, fumigated into the intake air stream prior to compression and introduction of the main fuel.
The two fuel parts—the main fuel comprising methanol and water, and the fumigant comprising dimethyl ether—may be transported through liquid pipelines from the point of manufacture, to the point of usage, such as a shipping terminal, train terminal, or remote community using a compression ignition engine to generate power. Moving bulk energy via liquid pipeline is a long standing and cost effective technique for moving large quantities of energy over long distances with minimum visual impact.
Whilst such techniques for moving fuel via liquid pipelines have their advantages, dimethyl ether cannot be transported in pipelines in liquid form under atmospheric pressure, and would require pressurisation to maintain the dimethyl ether in liquid form. It has been proposed by the present applicant to transport the dimethyl ether required for use in a fumigant as a component of a “pre-fuel composition” comprising methanol and dimethyl ether, and to separate the ether from the methanol, to generate a methanol-water main fuel part, and a dimethyl ether second fuel part, or fumigant.
The applicant has recognised that further improvements in fuel compositions, and/or the systems/procedures enabling them to be used commercially, could provide further advantages that would make them even more attractive as a replacement for traditional fuels.